Solving Exponential and Logarithmic Functions

Solve  $\log_2\left(x^2-2x+1\right)=2$ 

•  $\left\{3,1\right\}$  

•  $\left\{3,-1\right\}$  

•  $\left\{-3,1\right\}$  

•  $\left\{-1,-3\right\}$